TM 43-0139b.Air Leakage from Front of Gun. This condition is caused by the air valve not seating properly due to:(1)Foreign matter on the valve or seat.(2)A worn or damaged valve or seat.(3)A broken air valve spring.(4)A sticking valve stem due to lack of lubrication.(5)A bent valve stem.(6)A tightly closed packing nut.c.Material Leakage from Front of Gun. This condition is caused by the fluid needle not seating properly due to:(1)A worn or damaged fluid tip or needle.(2)Lumps of material or foreign matter lodged in the fluid tip.(3)A tightly closed packing nut.(4)A broken fluid needle spring.(5)An improper size needle.d.Jerky or Fluttering Spray.(1)In pressure or suction-feed guns, this condition is caused by air leakage into the material line due to:(a)A lack of sufficient material in the container.(b)Tipping the container at an acute angle.(c)An obstructed fluid passageway.(d)A loose or cracked fluid tip in the cap.(e)A loose fluid tip or damaged valve seat.(2)Conditions which apply only to suction feed are:(a)Material being too heavy for the suction feed.(b)A clogged air vent in the container lid.(c)A loose, dirty, or damaged fluid inlet connection.(d)The material feed tube (see figure 5-7) is resting on the bottom of the container.5-9